In the state of the art, the problems connected to coiling, on a continuously rotating mandrel, a long metal product, either rolled or drawn, traveling at high speed, to be wound in contiguous, adjacent and superimposed spirals, in a uniform manner, so as to form very compact coils, are known.
It is known that the operation to form the coil, so that the spirals are compact and uniformly distributed in every layer and for the whole longitudinal extension of the coil, is very delicate.
The problem of easily removing the finished coils from the mandrel is also known.
If the operation to remove the coil is not carried out correctly, defects may occur in the finished coils, such as for example the wound spirals may be released and/or the coiled roll may have a bad aesthetic appearance. Moreover, if the coil does not have a regular geometry, there are problems of stacking during the storage step, and also problems with installing the coil on the machine which uses the same, and problems with the correct unwinding of the coiled product.
The European patent EP-B-1.126.934 discloses a coiling machine which comprises suitable guides, substantially semi-cylindrical in shape, otherwise known as flaps or insertion blades. Said guides are able to intercept the metal product to be wound, as it arrives from the rolling mill or the drawing machine, and are able to facilitate the formation of the first spirals of the coil on the mandrel. This known coiling machine, which has the axis of the mandrel cantilevered, also comprises a mobile containing plate to frontally contain the coil, which plate cooperates with the terminal, cantilevered part of the mandrel, and which can be arranged in the following two limit positions: a first position for the formation of the coil, wherein the containing plate is orthogonal to the axis of the mandrel and coaxial therewith, and a second position wherein the containing plate is rotated by about 90° and arranged substantially parallel to the axis of the mandrel, in a position of non-interference with the path on which the finished coil is discharged.
Before starting to distribute the spirals on the mandrel, it is necessary that the metal product to be wound is correctly gripped on the mandrel itself; to this purpose, it is necessary to provide a device that performs the clamping of the metal product to the mandrel with great reliability, precision and repeatability.
The U.S. Pat. No. 3,592,399 discloses an apparatus to grip and wind the leading end, or head, of a rolled product onto a mandrel, rotating around a horizontal axis, which is provided with a first containing plate to contain the coil to be formed, arranged perpendicular to the mandrel, and with a second containing plate to contain the coil laterally. This second plate is autonomous and movable with respect to the mandrel between an operating position, wherein it is parallel to the first plate, and an extraction position, wherein it is arranged distant from the mandrel and rotated laterally by 90° with respect thereto. To be more exact, the second plate is mounted rotatable on a cylindrical supporting element, which in turn can rotate on a vertical support. In order to facilitate the beginning of the formation of the coil, the second containing plate has an axis of rotation which does not coincide with that of the mandrel and is provided with an annular groove which has a circular surface eccentric with respect to the outer surface of the mandrel. Due to the misalignment of the second containing plate and the mandrel, the two surfaces form a clamping channel with a variable section, into which the leading end of the rolled product to be wound enters and is locked. Moreover, in order to facilitate the clamping of the head at the start of the winding operation, the apparatus comprises a guide element, substantially semi-circular in shape, which in the operating position cooperates with the aforesaid clamping channel until the first spirals have been wound onto the mandrel. After some spirals have been formed, the guide element is distanced from the mandrel and raised to an inactive position. This apparatus does not allow to obtain a clamping of the leading end which is repeatable and reliable. If clamping does not occur, then we have a relative sliding occurs between the rolled product and the mandrel, so that coiling cannot begin. On the other hand, if the leading end becomes detached from the clamping channel, after the formation of a few coils (with the mandrel under torque and the rolled product already flowing), the tension of the coils is released, there is a consequent slippage between the parts and hence a blockage is created upstream of the coiling device, with all the problems that derive from this. Such a detachment during the coiling step is also facilitated by the progressive cooling of the rolled product which begins to shorten as it shrinks, starting from the leading end, thus causing a drawing effect that causes the leading end to come out of the gripping channel.
It is therefore of fundamental importance to be able to guarantee a secure and long-lasting clamping of the initial segment of the rolled product on the mandrel.
One purpose of the present invention is to achieve a coiling device for long metal products which will guarantee a considerable rapidity in installing the mobile frontal containing means that cooperate with the end part of the mandrel.
Another purpose of the invention is to guarantee the correct performance of the coiling process.
Another purpose pursued by the device according to the invention is to improve the quality of the final coil in terms of winding, compactness, density and holding capacity of the spirals.
A further purpose of the invention is to prevent damage and a reduced quality of the product.
It is also a purpose of the invention to simplify maintenance operations on said device.
The advantages achieved give a coil having a desired geometric profile which allows to exploit the storage space, also in height, to optimize the handling and transport steps, and gives a better functioning to the user machines, which can thus work at greater speed.
Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.